This invention relates to apparatus for removing the sprue slugs from plastic molding machines such as injection molding machines. This apparatus has a gripping arm and is mounted on the movable platen of the machine so that when the mold of the machine is opened, the gripping arm is guided by a cam control up to the sprue where gripping fingers located at the lower end of the arm grasp the slug for removal at the same time as the molded articles are being ejected from the mold.
In apparatus of this type, usually a crank arm, activated by a hydraulic cylinder, has a roller which runs along a guide rail connected to the stationary platen of the molding machine. The gripping arm is swivelled up and down by the movement of the cylinder. At the same time, a steering rod is guided by the roller running along the guide rail so that at the end of the downward movement of the arm, the gripping fingers are guided up to the sprue slug.
After gripping the slug, the fingers are moved away from the mold by extension of the steering rod, taken upwards by a swivelling up of the gripping arm and then swivelled out sideways by rotation of the arm. There, the gripping fingers open automatically and drop the slug into a hopper, suitably located above a grinding device. The slugs are then granulated and collected for reuse.
In this type of apparatus, the mechanical control for the crank arm poses a problem because the control rail fixed to the stationary platen of the machine has to be removed and subsequently reassembled each time a mold is changed. Also the rail has to be realigned each time with respect to the position of the fingers so that they will operate correctly at the various locations of the arm. This takes time and delays the start of a subsequent molding operation.
An object of the invention therefore is to provide a more simplified mechanism for removal of the slugs while at the same time making it easier to change a mold.